Railway signaling



Sept. 14,1926.

15%,??11 1.. o. GRONDAHL RAILWAY S IGNALING Original Filed Feb. 9, 19222 Shets-3heet 1 Fig. 2.

KNVENTOR 2 BM BY Q H- q ATTORNEY Sept. 14 1926. 1,599,711

. L. o. GRONDAHL RAILWAY SIGNALING Original Filed Feb. 9, 1922 2Sheets-Sheet 2 Fly. 8.

lNVE NTOR HQ ATTQRNEY Patented Sept. 14, 1926.

UITED STATESPATENT QFFEE.

LABS O. GRONDAHL, F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO UNION SVJ'ITCH8c SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OFPENNSYLVANIA.

RAILWAY SIGNALING.

My invention relates to railway signaling, and is particularly welladapted to signaling of the type wherein roadside s1gnals are governedby track circuits which in turn are controlled by the passage of cars ortrains along the track.

I will describe two forms of signaling apparatus embodying my inventionand will then point out the novel features thereof in claims.

In theaccompanying drawing, Fig. l is a diagrammatic view showing oneform of naling apparatus embodying my invention, while Fig. 2 is a viewshowing a modification of the apparatus shown in Fig. 1 and alsoembodying my invention. Figs. 3, a, 5, 6, 7 and 8 are views showingother forms of apparatus which may be employed to control the stop lampR, all of which also embody my invention.

Similar reference characters refer to similar parts in each of theseveral views.

Referring first to Fig. 1, the reference characters F and F designatethe track rails of a railway along which traflic normally moves in thedirection indicated by the arrow. plurality of successive track sectionsAB, BO, etc, the isolation of the track sections beingaccomplished, ashere shown, by insulated joints 2 in bothof the lines of rails, althoughany other suitable means of isolating the sections may be employedwithout departing from the spirit and scope of my invention.

Located adjacent the entrance end of each track section is a railwaysignal, designated by the reference character S with an exponentcorresponding to the location. In the form here shown, each signalcomprises three lamps G, Y and E, adapted when lighted to indicateProceed, Caution and Stop respectively.

Each track section is provided with a track circuit comprising asuitable source of current and a current receiving device, both of whichare connected across the track rails. As here shown, the source ofcurrent is the secondary 17 of a transformer designated by the referencecharacter T with an exponent corresponding to the location. Thesecondary is connected across the rails adjacent the exit end of thetrack section through a pole-changing device K for re- These rails aredivided into a versing the relative instantaneous polarity of thecurrent supplied to the rails, which pole-changing device is hereinafterexplained. The primary 4 of each transformer T is connected with atransmission line 5, which is constantly supplied with alternatingsignaling current by a generator 6. The current receiving device in theform here shown, is a transformer designated by the referencecharacter 1) with an exponent corresponding to the location, the primaryof which is connected across the rails cent the entrance end of thetrack section.

Each signal is controlled in part by two electron tubes E and-E, eachcomprising a vacuum bulb enclosing a filament 7 a grid 8, and a plate 9.The filaments 7 of the two bulbs at each signal location are constantlyheated by the secondary'13 of the adjacent transfo mer T, through acircuit which will be obvious from the drawing. Each electron tube E andE is provided with a grid circuit which is energized from the secondaryof the adjacent transformer D. Considering location B, for example, thegrid circuit for tube E is from the secondary of transformer D throughwire 18, grid and filament of tube E, and ondary of transformer D gridcircuit for tube E at this location is from the secondary of transformerD through wire 20, grid and filament of tube E, and Wire 19 to thesecondary of transformer D Each tube E and E is also provided with aplate circuit which is energized from the secondary 12 ofthe adjacenttransformer Considering location B, for example, the plate circuit forelectron tube E is from the left-hand terminal. of secondary 12, throughthe proceed lamp G, plate and filament of tube E, heating element 10 ofa thermo-sensitive relay J and heating element 10 of a thermo-sensitiverelay J to the middle point of secondary 12. The plate circuit for tubeE is from the right-hand terminal of secondary 12, through lamp Y, plateand filament of tube E, heating element 10 of relay J and heatingelement 10 of relay J to the middle point of second ary 12.

i It will be observed that at any given in- Similarly, the

stant the polarity of the grids 8 of the two tubes E and E are the same,whereas at any adjawire 19 to the sec- Application filed February 9,1922, Serial No. 535,194. Renewed A given instant the polarities of theplates 9 of the tubes E and E are opposite. It follows that when thetrack circuit current is of one relative polarity, the plate 9 of tube Ewill be positive with respect to the filament at the same instant thatthe grid 8 is positive with respect to the filament, so that ,the platecircuit for tube E is conductive,

whereas in tube E the plate 9 will be negative with respect to thefilament at the same instant that the grid is positive with respect tothe filament, so that the plate circ'uitfor this tube will benon-conductive; on the otherhand, when the polarity of the track circuitcurrent is reversed, the plate circuit for tube E will be non-conductiveand, the plate circuit for tube E will be con d'uctive. v

Each relay J and" J comprises the heat ing element 10, and athermo-sensitive element 11 responsive to variations in temperature byvarying its electrical resistance. Each thermo-sensiti've element'has anegative temperature coefiicient, and so it follows that when theheating element 10 is cold, that is, when it isnot supplied withcurrent, the resistance of the thermo-sensitive element 11 iscomparatively high, whereas, when the heating element 10 is hot, thatis, when it is supplied with current, the resistance of thethermo-sensitive element 11 is comparatively low.

The stop lamp R of each signal is directly connected with a secondary 1aof the adjacent transformer T, and this lamp is pro titled with a shuntwhich includes the thermossensi'tive element 11 of the adjacent relay J.Then the relay J" is energized,

its, resistance is so, low that lamp R is X- ti'nguished, but when thisrelay is de-enen gized its resistance is so high that sufilci'entcurrent flows through lamp R to cause this lamp toibe lighted;

The apparatus for controlling thepol'ari'ty of the track circuit currentis designated as a Whole by the reference character K with an exponentcorresponding to the location, and is in substance the same as theapparatus disclosed in Fig. 2 of Letters Patent of the United States No.1,555,495 granted to Lars 0. Grondahl, and Lester E. Spray on the 29thday of September, 1925-, for electrical apparatus. Briefly described,this apparatus is as follows: The middle point of transformer secondary17 is connected with one track rail F by a wire 23, whi1e the two outerterminals of this secondary are connected with the other rail, F throughwire 2& and the thermo-sensitive elements of two thermo-sensitive relaysJ and J respectively, both of which relays have negative temperatureco-efficients, The heating element 10' of relay J is connected in acircuit which includes a secondary winding 16 on the adjacenttransformer T and the secondy 22 of an adjacent transformer- H, thesetwo secondaries being so connected that they oppose each other. Theheating element 10 of relay J is connected with another sec,' ondary 22on transformer H. The two primary windings 21 and 21 of transformer Hare connected in series, and are included inacircuit which contains asecondary 15 on the adjacent transformer T and the thermo-sensitiveelement 11 of the adjacent relay J The primary 21 and secondary 22 oftransformer H are inductively independ ent of the primary 21 andsecondary 22. hen relay J is energized, current ofconsiderable value issupplied to transformer H by secondary 15, so that relay J t isenergizedby current from secondary 22*. The voltage of secondary 22 substantiallyneutralizes that of secondary 16, however,'so that relay J isfile-energized. The resistance of relay J is then low, whereas theresistance of relay J is high, so that current is supplied to the trackrails of the corresponding-section by the right-hand half of transformersecondary 1?. 0n the other hand, when relay 5 is tie-energized, thecurrent furnished by secondary 15 is negligible, so that the current inthe primaries of transformer H is low. Relay J isv then d'e-energized,whereas relay J is energized due to current which is now supplied bysecondary 16. The resistance of relay J is, consequently, high, but theresistance of relay J is low,so that current is supplied to the trackrails by the left-hand half of secondary 17. It will be seen therefore,that current of' one relative instantaneous polarity or the other is,sup? plied to the track rails of' each section aocording as thethermo-sensitive relay J at the exit end of each section is energized or(ls-energized.

The operation of the apparatus shown in Fig. 1, is as follows:

As here shown, the track section, to the left of location A is occupiedby a car or train VF, so that the supply of current to the primary oftransformer D is discontinued or reduced to an extremely low value. Bothof the grid circuits at location A are consequently de-energized, sothat both plate circuits are non-conductive, with the result that bothlamps G and Y at this location a-reextinguished. There being no currentin: eitl i-v er plate circuit, it follows that the relays J and J theheating elements of which are common to the plate circuits, are both de-energ-ized. The resistance of relay J" is consequently high, so thatthe stop lamp-R ofsignal S is lighted, The resistanceofrelay J islikewise hi gh, so that in the pole-changing device K relay J isenergized and relay J is de-energized, with the result that the tracksection AB is supplied with current from. the left-hand half oftransformer secondary 17. The relative polarity of this current is Cirsuch that the electron tube E at location B is conductive and theelectron tube E at this location is non-conductive. It follows that lampY of signal S at location B is lighted and lamp G is extinguished. LampR is likewise extinguished because relay J is energized by the currentflowing in the plate circuit of tube E. Relay J 2 at location B is alsoenergized, so that in the pole-changing apparatus K the relay J isenergized and the relay J is de-energized. This causes current from theright-hand half of secondary 17 of transformer T to be supplied tothetrack circuit for section BC, and the relative polarity of thiscurrent is such as to render the tube E at location O conductive and thetube E at this same location non-conductive. Lamp G of signal S isconsequently illuminated and lamp Y is extinguished, lamp R also beingextinguished because relay J is energized by the current in the platecircuit for tube E.

Referring now to Fig. 2, the apparatus shown in this View is the same asthat shown in Fig. 1, except that the thermo-sensitive relays J and J 2are removed from the common return wire for the plate circuits ofelectron tubes E and E and are placed in series directly across thesecondary of the adjacent transformer D. It follows that each pair ofrelays J and J 2 will be energized when the corresponding track sectionis unoccupied, and de-energized when such track section is occupied, sothat these relays are energized and Clo-energized under the sameconditions as in Fig. 1.

The operation of the system shown in Fig. 2 will be readily understoodin view of the detailed explanation set forth hereinbefore of theoperation of the system shown in Fig. 1. i In Figs. 1 and 2, it will beobserved that the stop lamp R is connected across a transformersecondary 14, and that the thermosensitive element of relay J isconnected in multiple with the lamp, the control being such that whenrelay J is 'de-energized the lamp is lighted, but that when' this relayis energized suliicient current is shunted away from the lamp toextinguish the lamp. ther arrangements for the control of the stop lampare illustrated in Figs. 3, 4, 5, 6, 7 and 8.

Referring to Fig. 3, the lamp R and the thermo-sensitive element ofrelay J are connected in multiple across secondary 14 as in thepreceding Views, but in series with the lamp is the thermo-sensitiveelement 11 of an additional relay J 5 the heating element 10 of which isalso connected across second-' ary 14. A resistance 25 is preferablyincluded in the circuit as shown. l/Vhen relay J is energized, theamount of current flowing in the heating element of relay J 5 is sosmall that this relay is also de energized,

this relay decreases to such extent that the lamp becomes lighted. Thisarrangement has an advantage over thoseshown in Figs. 1 and 2 in thatthe load on relay J is reduced and a smaller change in voltage at thisrelay accomplishes'the desire-d'result;

In Fig. 4 the apparatus for the control of lamp R embodies thepotentiometer principle. An additional secondary 26 on transformer T isconnected across a resistance :27, the thermo-sensitive element of relayJ being included in such. connection, whilethe circuit for secondary 14includes the lamp R and a portion of resistance 27. When relay J isenergized, the drop across the portion of resistance 27 which is inseries with lamp R balances the voltage of secondary 14 so that the lampis extinguished. When relay J becomes tie-energized, the current inresistance 27 is reduced, so that the voltage across the left-handportion of this resistance is reduced and no longer balances the voltageof secondary 14; lamp R then becomes lighted. r a

Fig. 5 is the same as Fig. 4 except that an additional thermosensitiverelay J is introduced for the same reason as in Fig. 3, so that thecontrol of lamp R may be effected by a smaller change in the voltageacross the left-hand portion of resistance 27. a

The apparatusshown in Fig. 6 embodies a When relay J becomes detheVVheatstone bridge principle. That is i to say, the four resistance armsof the bridge are formed by three resistances 28, 29 and 30 and thethermo-sensitive element of relay J, while thebridge member is the lampB. When relay J is energized the bridge is balanced so that no currentflows in lamp R, but when relay J becomes de-energized thebalance isdestroyed and sailicient current is then supplied to lamp R to lightthis lamp.

The apparatus shown in Fig. 7 is the same as that of Fig. 6 except thata step-up transformer 81 is introduced between the bridge to increasethe voltage apand the lamp R plied to the lamp when the bridge isunbalanced.

The apparatus shown in Fig. Salso embodies the lVheatstone bridgeprinciple, but differs from Fig. Gin that the lamp is controlled by tworelays J and J the thermosensitive elements of which constitute twoopposite arms of thebridge. The remaining arms are resistances 29 and32. l/Vhen the relays are energized, the bridge is balanced and the lampis extinguished. When the relays become de-energized, current will flowfrom secondary 14 through resistance 29', lamp 1%,, and resistance 32to. secondary 1,4, and so the lamp will become lighted. It desired, atransformer may be interposed between the bridge and the lamp as inAlthough I have herein shown and de scribed only certain forms otsignaling apparatus embodying my invention, it is understood thatvarious changes andmodifications may be made therein ithin. the scope Tsuch manner that the gridslrave the same polarity at any given instant,a transformer the primary of which is constantly supplied with currentoi the same frequency as that supplied to said track rails, a platecircuit I for each tube one of which extends from the middle point otthe secondary or said trans former to one secondary terminal and theother of which extends from the said middle point to the other secondaryterminal, a

proceed signal and a caution signal controlled by said two platecircuits respectively, a device includedin. circuit with said secondaryand commonto saidtwoplate circuits and responsive to variations in thecurrent strength therein, and. a stop signal controlled by said device.

2'. In combination, a section of railway track, a source of alternatingcurrent reversibly connected with the rails of said section, twoelectron tubes, a grid circuit for each tube energized from said trackrails in such manner that the grids have the same polarity at any given.instant, a transformer the primary of which is constantly supplied withcurrent of the same iirequency as that supplied to said track rails, aplate circuit for each, tube one of which extends from: the middle pointof the secondary of said transformer to one secondary terminal and theother of which extends from the said. middle point to. the othersecondary terminal, a proceed signal and a caution signal controlled bysaid two plate circuits respectively, a relay comprising a heatingelement included in circuit with said secondary and common to the twoplate circuits and a member of thermo-sensitive substance, and a stopsignal. controlled by said substance.

3. In combination, a section of railway track, a source of alternatingcurrent reversibly connected with the rails oi said section, twoelectron tubes, a grid circuit for each tube energized from said trackrails, two plate circuits onetor each tube and including aconductorcommon to the two, the

neonate circuits for said tubes being so connected that one platecircuit or the other is conductiveaccording as the current supplied toeach tube energized trom said track rails,

two plate circuits one for each tube and including a conductor common tothe two, the

circuits for saidtubes being soiconnected that with track current of onerelative polarity the grid; and plate of onetubeare positive at the sameinstant and the grid and plate of the other tube are positive andnegative at the same instant while with track current of the otherrelative polarity the grid and plate of theifirst tube are positive andnegative at the same instant and, the grid and plate of the second tubeare both positive at the same l-nstant, a device controlled by theconductor common to the two plate circuits and responsive to currentamplitude variations therein, and signaling means governed by said two;plate circuits and by said device.

5;, In combination, a section of railway truck, a source 0t alternatingcurrent reversibly connected with the rails: of said section, twoelectron: tubes, agrid circuit for each tube energized from said trackrails, two plateci-rcuits one for each tube and including a conductorcommon. to the two, the circuits for said tubes being so connected thatone plate circuit or the other is conductive according as the currentsupplied to the track rails is of oneinstantaneous relative polarity orthe other, a device controlled by the conductor common liOz the twoplate circuits and responsive to current amplitude variations therein,and signaling means governed by said two plate circuits and by saiddevice.

6. In combination, a section of railway track, it source of alternatingcurrent reversibly connected; with the rails of said section, each tubeenergized from said track rails, two plate circuits one for each tubeand including a conductor common to the two, the circuits for said tubesbeing so connected that one plate circuit or the other isconductiveaccording as the current supplied to the track rails is of oneinstantaneous relative polarity or the other, a heating element includedin said conductor common to the two plate circuits, a thermo-sensitiveelement subjected to variations in the temperature of saidv heatingelement, and signaling means two electron tubes, a grid circuit forcontrolled by said two plate circuits and by said thermo-sensitiveelement.

7. In combination, a section of railway track, a source of alternatingcurrent 1eversibly connected with the rails of said section, twoelectron tubes, a grid circuit for each tube energized from said trackrails, two plate circuits one for each tube and including a conductorcommon to the two, the circuits for said tubes being so connected thatone plate circuit or the other is conductive according as the currentsupplied to the track ails is of one instantaneous relative polarity orthe other, a relay comprising a thermo-sensitive element and a heatingelement included in-said common conductor, a proceed lamp and a cautionlamp included respectively in said two plate circuits, a stop lampconnected with a source of current, and a shunt around said stop lampincluding the thermo-sensitive element of said relay.

8. In combination, a section 01' railway track, a source of alternatingcurrent reversibly connected with the rails of said section, twoelectron tubes, a grid circuit for each tube energized from said trackrails, two plate circuits one for each tube, the circuits for said tubesbeing so connected that one plate circuit or the other is conductiveaccording as the current supplied to said track rails is of one relativepolarity or the other, a proceed and a caution signal controlled by saidtwo plate circuits respectively, and a stop signal responsive to thepresence and absence of vehicles in said track section.

9. In combination, a circuit including a signal device and a source ofcurrent, a shunt path around said signal device including thethermo-sensitive element of a thermosensitive relay, and means governedby railway traflic for controlling the supply of current to the heatingelement of said relay.

10. A railway signaling system c0mprising a signal including a stoplamp, a circuit including said lamp and a source of current, a shuntpath around said lamp including the thermo-sensitive element of athermo-sensitive relay, and trafiic governed means for controlling thesupply of current to the heating element of said relay.

In testimony whereof I aflix my signature.

LABS o. GRONDAHL,

